The literature is rich in data pertaining to circuitry which can be utilized in the method and system herein presented, such as band reject, band pass and low pass filters, frequency controlled switches, and signal combiners. There is no attempt herein to claim specific circuitry, but rather the claim is to a new use for such circuitry to provide a system and method for enabling the fee-enforceable operation of subscription available electromagnetically transmitted modulated information communication via specially equipped transmitters and receivers.
Equipment with which a typical 1800 Hz (100 Hz bandwidth) tone can be combined with the voice frequency signal for transmission over FM-SCA facilities, and which provides receivers with trimmable band reject capability, is available in the market and utilizes circuitry of a type readily available in the industry. The available equipment does not, however, profor the use of widely variable control signal frequencies nor for the use of user changeable, easily mailable receiver tuning components. The improvement herein provides for such enforcement enhancing attributes. The inventor knows of no prior art which performs or obviates the performance of the function herein claimed.
Other available systems utilize receiver specific control coded signals to turn on or off receivers equipped with proper decoding circuitry; however, such systems cannot effect the operation of home-built receivers which do not include the decoder control circuitry, hence, are not well suited to enforceable access control.